Presentation slides on best practices for building social web applications by Luke Wroblewski, Principal Designer, Yahoo! Inc. at the IxD Symposium IA Summit 2006.  The presentation begins with definitions of community: "People United by shared interests and goals."  A community is comprised of Content - products, actions (features), and interest (compelling content), and Social Behaviors - reputation and identity, communication, and rituals and groups. The people who make up a community can be divided into three groups: Creators (1%), Synthesizers (10%), and Consumers (100%). Communities enable people to share and contribute, and can create the following benefits: filtered information, new content, increased engagement, invested customers, collaborative innovation, and inclusion, but can have drawbacks: "social" features can distract from content, quality of contributions can be low (and worse, spam), power laws form that give dominant influence to the few, and privacy and security issues can arise.

Best Practices:

• Enable Identity:
• Welcome people
• Anonymity can be a Death Sentence due to lack of accountability and reputation
• enable Personal Branding
• allow people to show their Accomplishments
• provide Social Incentive
• Focus on the Epicenter, dont lose sight of primary content and goals
• Provide for Creators, Synthesizers, and Consumers
• CSC personality types do not easily migrate between groups
• Leverage differences to maintain balance
• Design Systems
• Extensible
• Think "Ecosystem": cycles and movement of content
• Structured
• Objects & Actions
• Constraints Balance Systems
• Quality Control
• Barriers to Entry
• Game Design
  

Note: The above best practices are illustrated with some great examples (from Yahoo! properties, of course) and diagrams, so I highly recommend downloading the pdf.